Knife sharpener



Sept. 7, 1948. B. FQSCHMIDT KNIFE SHARPENER Filed Sept. 10, 1945 BENJAMIN F. SCHMID 7:

1N VEN TOR.

Patented Sept. 7, 1948 UNITED STATES PATENT OFFICE KNIFE SHARPENER Benjamin F. Schmidt, Los Angeles, Calif. Application September 10, 1945,.Serial No. 615,271

Claims. I

My invention relates to knife Sharpeners, and has particular reference to a sharpener of simple construction in which a cutter is held in a convenient holder through which a knife may be drawn to dispose the edge of the knife against a cutting edge of the cutter. 7

It is an object of my invention to provide a knife sharpener which comprises essentially a block of material adapted to hold a short strip of relatively hard cutting material in a predetermined angular relation to one or more knife guiding slots through which a knife may be drawn to be guided in such fashion as to present the edge of a knife blade to the cutting surface of the cutter at the correct angle to cause the cutter to sharpen the-knife blade edge.

Another object of m invention is to provide a knife sharpener of the character set forth, in which the cutter is constructed as an elongated strip of relatively hard material clamped in place in a bore on the holder or support, and inwhich one or more slots are formed in the support through which the knife blade may be drawn, the slots being disposed in a plane intersecting the edge of the cutter at a fixed acute angle.

Another object of my invention is to provide a knife sharpener of the character described, in which the cutter is disposed with its cutting edge at an obtuse angle to the direction of the movement of a knife blade through the slots.

Another object of my invention is to provide a knife sharpener of the character set forth, wherein the slots are formed with tapering sides to accommodate knife blades of different thickness, and which means is employed to urge the knife blade against the wall of the slot most distant from the cutter to aid in guiding the knife blade through the slot.

Another object of my invention is to provide. a knife sharpener of the character set forth, in which the cutter member is formed as an elongated strip of relatively hard material of either triangular or trapezoidal cross-section to present sharply angled edges to the knife blade guiding slots.

Another object of my invention is to provide a knife sharpener of the character set forth, in which, in addition to the cutter element there is provided a sharpening stone conveniently located to complete the sharpening of the knife blade after the blade has been partially sharpened by the cutting element.

Other objects of my invention will be apparent from the study of the following specifications,

read in connection with the accompanying drawings, wherein:

Fig. 1 is a perspective view of a knife sharpener constructed in accordance with my invention;

Fig. 2 is a fragmentary front elevational view of the knife sharpener shown in Fig. I;

Fig. 3 is a fragmentary top plan View of a modified form of sharpener embodying the principles of my invention;

Fig. 4 is a transverse sectional view taken along the line IV-IV of Fig. 3;

Fig. 5 is a transverse sectional view taken the line V-V of Fig. 4;

Fig. 6 is a top plan view of a modified form of sharpener embodying the principles of myinvention; and

Fig. 7 is a front elevational View of the sharpener shown in Fig. 6.

Referring to the drawings, I have illustrated in Figs. 1 and 2' one form of sharpener which preferably comprises a body I which maybe constructed as a block or casting of metal, plastic, or the like, adapted to be held in a stationary position by means of a suitable handle 2. The block I comprises a support for a cutter 3 which, in the form illustrated in Figs. 1 and 2, comprises an elongated strip of hard steel having a triangular cross-section disposed within a vertically extending bore 4 extending from the top surface of the block or body I. The bore may be circular in cross-section, though I prefer to use a shape which will include a plurality of angular enlargements 5 of the bore 4, each of which defines the apex of a triangle, or to be more exact, the angular intersection of three vertical planes passing through the upper surface of the block I. The forward notches or enlargements 5 of the bore are preferably located at the .base of the triangle as viewed from the top surface of the block, this :base extending parallel to the front and rear walls 6 and l of the block so that two of the angular edges of the cutter 3 will be disposed in the plane of this base. 1

The block I is formed with one Or more slots along 8 and 9 extending from front to rear of the block,

and extending from the top surface of the block, the slots extending along planes which intersect the bore 4 at an acute angle, the intersection occurring adjacent the lower end of the bore, and hence adjacent to the lowermost end of the cutter strip 3 in, such manner as to expose within the slot a portion of the angular or sharpened edge of the cutter 3.

Each slot may be effectively employed as an guide into which a knife blade may be placed and drawn therealong with the edge of the blade disposed in contact with the sharpened edge of the cutter at the correct angle to cause the cutter to scrape the material of the knife blade along an angular surface such as to re-sharpen the edge of the blade.

As will be particularly noted by an inspection of Figs. 1 and 2, the slots 8 and 9 do not have parallel sides, but instead each of the slots is formed with a slight taper to readily accommodate knives of different thickness of blade, but in order that the blade may be accurately guided into contact with the cutter, I prefer to use in each of the slots a pin Ill disposed in a cross-bore H in such fashion that the end of the pin projects into the slot and is urged toward such projecting position by means of a spring l2.

Where two slots are employed such as is illustrated at 8 and 9, one of the slots should be located on one side of the bore 4 and the other at the opposite side of the bore, the angle of the plane of each of the slots to the longitudinal axis of the bore being at the same but opposite acute angle. Thus by drawing the blade through one of the slots 8, one side of the blade edge will be sharpened by one edge of the cutter 3, and then by drawing the knife blade through the other of the slots, the opposite side of th blade edge will be sharpened, resulting in a feathering of the blade material into a sharp angled cutting edge.

When two slots are used, the pins Ill which project into opposite slots may be each formed with an enlarged head l3 and an inwardly projecting extension l4, while the spring l2 extends between the extensions ll of both pins and acts to urge both of the pins into their innermost projecting positions within the opposed slots 8 and 9.

The cutter element 3 may be retained within the bore 4 by any suitable means, though I prefer to employ either a set screw l5 shown in Figs. 1 and 2 which may be tightened against the flat surface of the cutter element presented toward the front face of the block I or by means of a spring I6 as shown in Figs, 4 and '7. Thus, when a cutter of triangular cross-section is employed, the apex of the triangle opposite to the forward face of the cutter, will be pressed into the rearmost notch 5 of the bore, while the sides of the cutter leading to the apex will be pressed tightly against the forward sides of the two angular notches disposed in the plane parallel to the front face of the block. By making th length of the cutter 3 less than the depth of the bore 4, the cutter may be shifted readily up or down to present new cutting surfaces in the event the contact surface of the edge becomes dulled.

The handle 2 may be readily employed as a means for mounting a cylindrical hone or sharpening stone which may be employed to complete the sharpening operation, the stone I! being cemented in a semi-cylindrical depression formed in the handle 2.

In Figs. 3, 4, and 5 I have illustrated a slightly modified form of construction in which the bore 4a is formed upon a longitudinal axis which extends at an acute angle relative to the front face of the block I, that is, the bore extends forwardly of the block as it progresses into the block. Thus, the cutter 3 will be disposed with two of its angular edges located in the same plane, one axis of which is parallel to th front face, but the other axis of which extends downwardly and forwardly at an acute angle to such front face.

Thus, the act of drawing the knife blade through a slot will cause the sharpened edge of the cutter to engage the edge of the knife blade, and by reason of the frictional and abrasive contact tend to draw the knife downwardly in the slot and to thus facilitate the sharpening operation without requiring downward pressure to be manually exerted upon the blade.

In Figs. 6 and '7, I have illustrated a still further modified form of the invention in which the handle 2a extends laterally and upwardly relative to the upper surface of the supporting block la. The block la in this form of the invention, includes the bore 4 having angular projections 5 disposed in the same manner as described in reference to Figs. 1 and 2, but the cutting element 3a is illustrated as having a cross-sectional shape substantially rectangular, though if desired, the shape of the cutting blade may be trapezoidal in order to provide a pair of angularly sharpened cutting edges extending in intersecting relation with the slots 8a and 9a.

It will be apparent from the foregoing that I have provided a knife sharpening device which is extremely simple in construction, and which provides for employment of sharpening elements or cutters which may be readily-removed and replaced when they become dull. When a cutter of triangular cross-section is used, the effective life of the cutter may be extended by removing the cutter and replacing it with different ones of the apices of the triangle in the forwardmost notches 5 of the bore 4. Similarly, if the cutter is of rectangular cross-section, it may be removed and reversed in order to present new corners or angular cutting surfaces to knife blades drawn through the guiding slots 8 and 9, or 8a and 9a.

If the body I is constructed of metal, it may be advisable to employ strips of leather, rubber or other cushioning material It at the bases of the slots 8 and 9 to prevent inadvertent dulling of the blade edge by metallic contact at the front or rear ends of the slots.

While I have shown and described the. preferred embodiment of my invention, I do not desire to be limited to any details illustrated or described herein except as defined in the ap pended claims.

I claim:

1. In a knife sharpening device, a body member having a top surface, a bore extending from said surface into the body, a slot extending from said surface at one side of said bore, said slot being disposed in a plane intersecting the bore at an acute angle, a cutter comprising a strip of relatively hard material disposed in said bore, said striphaving a cross-section of such geometrical shape as to provide a corner projecting into the slot whereby a knife blade disposedin said slot and drawn therealong will engage the exposed corner of said cutter, said slot tapering from a large width adjacent the top surface of said body to a smaller width adjacent the bottom of the slot, and means extending into said slot for engaging and urging a knife blade disposed in said slot against that wall of the slot most distant from the bore.

2. In a knife sharpening device, a body member having a top surface, a bore extending from said surface into the body, a pair of slots extending from said surface one at each side of said bore, each of said slots being disposed in planes intersecting the bore at acute opposite angles, a cutter comprising a strip of relatively hard material disposed in said bore, said strip having a cross-section of such geometrical shape as to provide a pair of corners, one projecting into each of said slots whereby a knife blade disposed in either of said slots and drawn therealong will engage the corner of said cutter exposed in said slot, each of said slots tapering from a larger width adjacent the top surface of the body to a lesser width adjacent the bottom of the slot, a cross bore extending laterally across said body adjacent the upper ends of said slots, a pair of pins in said cross bore, each projectin into one of said slots, and spring means urging said pins into projecting positions to engage and. urge a knife blade in said slot against the Wall of said slot most distant from the bore.

3. In a knife sharpenin device, a body member having a top surface, a pair of slots extending from said surface in converging planes disposed at acute angles to said surface, a bore extending from said surface and intersecting said slots adjacent the bottoms of said slots, said bore having a cross-sectional geometric shape defining at least a pair of corners disposed in a single plane extending at right angle to one axis of the planes of each of said slots, said corners respectively intersecting said slots, a cutter comprising a strip of relatively hard material disposed in said bore and having a cross-sectional shape defining a fiat surface disposed in the plane of said corners and sharpened edges intersecting said slots, and resilient means extending into said bore to engage said cutter and to hold said cutter in variably adjustable positions along the length of said bore.

4. In a knife sharpening device, a body meinber having a top surface, a pair of slots extending from said surface in converging planes disposed at acute angles to said surface, a bore extending from said surface and intersecting said slots adjacent the bottoms of said slots, said bore having a cross-sectional geometric shape defining at least a pair of corners disposed in a single plane extending at right angle to the line of intersection of the planes of each of said slots, said corners respectively intersecting said slots, a cutter comprising a strip of relatitvely hard material disposed in said bore and having a cross-sectional shape defining a flat surface disposed in the plane of said corners and sharpened edges intersecting said slots, and a spring extending into said bore and bearing against said flat side of said cutter to hold the cutter in variably adjustable positions in said here.

5. In a knife sharpening device, a body member having a top surface, a pair of slots extending from said surface in converging planes disposed at acute angles to said surface, a bore extending from said surface and intersecting said slots adjacent the bottoms of said slots, said bore having a cross-sectional geometric shape defining at least a pair of corners disposed in a single plane extending at right angle to one axis of the planes of each of said slots, said corners respectively intersecting said slots, a cutter comprising a strip of relatively hard material disposed in said bore and having a cross-sectional shape defining a flat surface disposed in the plane of said corners and sharpened edges intersecting said slots, and cushioning non-metallic material disposed in the bottoms of said slots to prevent contact between a knife edge and the body material.

BENJAMIN F. SCHMIDT.

REFERENCES CITED lhe following references are of record in the file of this patent:

UNITED STATES PATENTS Number 

